The present invention relates to a magnetic resonance signal receiving apparatus and a magnetic resonance imaging apparatus, and more particularly to a magnetic resonance signal receiving apparatus using a plurality of receiving coils defining a phased array, as well as to a magnetic resonance imaging apparatus using such a magnetic resonance signal receiving apparatus.
In a magnetic resonance imaging apparatus, a receiving coil is placed in the proximity of an imaging object, so as to measure magnetic resonance signals as close to the imaging site as possible in order to improve the signal to noise ratio (SNR) of the signal.
A typical example of the receiving coil of this type is the receiving coil that is used for imaging the spine. The receiving coil is configured of a plurality of coil loops forming a phased array. Since by forming a phased array, each of coil loops may operate respectively as a single coil, an appropriate combination of coil loops may be selected in accordance with the area to be imaged, to image a desired part of spine such as cervical spine, thoracic spine, or lumbar spine and the like.
In a receiving coil as have been described above, there has been a problem that the configuration of selector means for selecting a combination of coil loops may become complex.
It is therefore an object of the present invention to provide a magnetic resonance signal receiving apparatus which may simplify the configuration of coil loop selector means, as well as a magnetic resonance imaging apparatus which may use such a magnetic resonance signal receiving apparatus.
In a primary aspect of the present invention for solving the problem as have been described above, the present invention provides a magnetic resonance signal receiving apparatus, comprising: a plurality of receiver coils defining a phased array; capacitors each provided in series in a loop of the plural receiver coils; inductors each connected in parallel to the capacitors through a pair of diodes connected in parallel in oppositing polarity each other; diodes each provided in series in a loop of the plural receiver coils; and a bias controlling means for enabling receiver coils selected from within the plural receiver coils and disabling others by controlling independently the bias of the diodes.
In a secondary aspect of the present invention, the present invention provides a magnetic resonance imaging apparatus, comprising: static magnetic field formation means for forming static magnetic field in a space housing an imaging object; gradient magnetic field forming means for forming gradient magnetic field in the space; radio frequency magnetic field forming means for forming radio frequency magnetic field in the space; measuring means for measuring magnetic resonance signal from the space; and image generating means for generating images on the basis of the measured the magnetic resonance signals; and the measuring means comprising a plurality of receiver coils defining a phased array; capacitors each provided in series in a loop of the plural receiver coils; inductors each connected in parallel to the capacitors through a pair of diodes connected in parallel in oppositing polarity each other; diodes each provided in series in a loop of the plural receiver coils; and a bias controlling means for enabling receiver coils selected from within the plural receiver coils and disabling others by controlling independently the bias of the diodes.
In the present invention, each of receiver coils are controlled to be enabled or disabled at the time of RF excitation as well as at the time of reception of magnetic resonance signal by the application of bias to the diodes in order to select a combination of receiver coils effective for receiving the magnetic resonance signals. Also, the parallel resonance circuit made of a capacitor and an inductor may disable each receiver coil at the time of RF excitation.
In accordance with the present invention, a magnetic resonance signal receiving apparatus with simplified arrangement of coil loop selecting means, as well as a magnetic resonance imaging apparatus using such a magnetic resonance signal receiving apparatus may be achieved.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.